Gravitational Production of a Conformal Dark Sector

TL;DR

This paper investigates how gravitational interactions can produce dark matter in a conformal dark sector, providing analytical formulas and exploring various phenomena, with a focus on dark glueballs and holographic duals.

Contribution

It offers a general analytical framework for gravitational production of conformal dark sectors, including scale-invariant regimes and strongly coupled theories with holographic duals.

Findings

Gravitational production can generate viable dark matter candidates.

Dark glueballs are suppressed in gravitational production, making them plausible DM candidates.

Results extend to strongly coupled CFTs and holographic models.

Abstract

Dark sectors with purely gravitational couplings to the Standard Model are unavoidably populated from the SM plasma by graviton exchange, and naturally provide DM candidates. We examine the production in the relativistic regime where the dark sector is approximately scale invariant, providing general analytical formulas that depend solely on the central charge of the dark sector. We then assess the relevance of interactions that can lead to a variety of phenomena including thermalisation, nonperturbative mass gaps, out-of-equilibrium phase transitions and cannibalism in the dark sector. As an illustrative example we consider the dark glueball scenario in this light and show it to be a viable DM candidate due to the suppression of gravitational production. We go on to extend these results to strongly coupled CFTs and their holographic duals at large-N with the dark dilaton as the DM candidate.